.Iadd.This application is a reissue of U.S. Pat. No. 4,295,682 issued Oct. 20, 1981 on application filed on Nov. 1, 1979. .Iaddend.
In copending application Ser. No. 945,303 filed on Sept. 25, 1978 applicant found it possible through the use of a pivoted locking plate coaxial with the main hinge pivot, capable of angular movement relative to both seat and back rest hinge members, together with a ratchet having an arcuate toothed sector pivotally connected to the seat hinge member and with a differential translation connection between locking plate and ratchet plate, together with the provision of an inertia latch pivotally connected to the back rest hinge member interacting with the locking plate, to achieve desired operation, under presence or absence of deceleration, including the combined advantages of fine small increment adjustment over a full range of seat recliner accommodation together with automatic release for forward tilting to facilitate rear seat passenger convenience in entering and leaving the vehicle. In a further copending application Ser. No. 072,013 filed on Sept. 4, 1979, applicant discloses a seat back adjuster which employs a combination of improved accuracy in stop location for extremity of adjustment together with a special provision at each end of the ratchet sector which cooperates with the pawl extremities to prevent the misengagement which could otherwise result from overpassing the last incremental position at which full tooth engagement can be achieved. Such provision, in case of overtravel beyond the last increment for full tooth engagement, assured positive back travel to the last increment position in response to pawl engagement. Such provision together with a translation overdrive linkage between the seat back and adjustment ratchet achieves a substantial improvement in fineness of adjustment to approximately one degree of increments of seat back adjustment. .Iadd.The need for (1) forward tilting of the seat back to accommodate ingress and egress of rear seat passengers in two door automotive vehicles; (2) a safety provision for preventing such forward tilting under accident or emergency deceleration conditions; and (3) permitting forward tilting when the vehicle is stationary without requiring manual release of a latch lever; has led to development and use of inertia latch controls. Such controls normally respond to gravity in releasing the latch upon forward initial tilting of the seat back when the vehicle is stationary, and respond to deceleration inertia to assure latch engagement under predetermined vehicle deceleration values.
These inertia latches have been located on the pivoted bracket for either seat or back rest, with the cooperating reaction element on the other bracket and with the center of gravity normally offset in both horizontal and vertical directions to provide a gravity bias toward releasing the latch and a deceleration inertia bias toward engaging the latch. In some cases the inertia element has been normally positioned in an unlatching attitude requiring inertia responsive pivoting to produce latch engagement.
However, in preferred prior embodiments, an extension of the inertia element has been adapted to engage an actuating surface upon return of the seat back to its operative sitting position which overcomes gravity bias and pivots the latch element to a latching attitude. In these units deceleration inertia is required only to maintain such latching engagement attitude upon initial seat back tilting, rather than to produce latching pivotal movement, thereby reassuring proper latching engagement under all required conditions, notwithstanding variable frictional resistance in the pivotal mounting through accumulation of dirt or otherwise--in other words to assure a "failsafe" mode of operation. In these units positive stop means independent of the inertia latch have been employed to limit backward pivotal movement between seat and back rest hinge members at the operative setting position.
The requirement for completely free pivoting action of the inertia element to meet operating specifications under various conditions--e.g. nose down parking, which reduces the gravity release bias, or adjustment of the seat to a reclined position, which reduces the horizontal inertia moment arm--has led to certain problems of noise from inertia latch rattling as well as the need for coordinating tolerances of the back stop elements with surfaces determining the normal position of the inertia element. Even when the inertia element engages a surface establishing latching attitude in opposition to gravity bias, there is potential for rattling from any looseness in the pivot; or a potential for frictional binding at the pivot where antirattle close clearances are incorporated in the design.
Examples of the most relevant prior art of which applicants are aware include inertia latch constructions shown in the following issued U.S. Pat. Nos.: 4,223,946; 4,252,370; 4,318,569. None of these patents disclose an inertia latch operative per se to provide a back rest stop. .Iaddend.